Re: 2013 HSC physics marathon
\begin{align*}&\Delta E_{p}=GmM\left ( \frac{1}{r_{2}}-\frac{1}{r_{1}} \right )\\&6.67\times 10^{-11}\times mM \left ( \frac{1}{1 \times 10^{7}}-\frac{1}{2 \times 10^{7}} \right )=1 \times 10^{6}\\&\therefore mM=2.999 \times 10^{23}\\\\&\Delta E_{p}=6.67\times...